In this work, fibrous very high molar mass polyethylene was prepared by Cp2TiCl2, which was supported on methylaluminoxane (MAO) pretreated mesoporous silica fiber. After the polymerization, an "ordinary" washing procedure was not sufficient to remove the aluminum residues of the cocatalyst MAO from the polymerization product. When hydrochloric acid was used in the termination of the polymerization, the aluminum existed as [Al(H2O)(6)]Cl-3, the presence of which causes additional signals to DSC and XRD grams of the polyethylene. These signals have previously been interpreted to be attributed to the extended chain crystal structure of the polyethylene. (C) 2004 Wiley Periodicals, Inc.